A fastener on a pipe fitting, e.g., a hoop, also called as a lug clip and provided with a circular inner ring, is widely applied to life. At present, a Chinese patent with an application number of CN201380025000.0 discloses a lug clip; and the lug clip is provided with a clamping belt in which a lug-shaped fastening part is formed, and two legs extending outwards and mutually connected through a rib plate.
Because the inner diameter of the lug clip is greater than the outer diameter of a pipe fitting, the lug clip is quite liable to loose in case of being sleeved on the pipe fitting, however, if the inner diameter of the lug clip is directly reduced to be equal to the outer diameter of the pipe fitting, surface-surface friction will be formed between the pipe fitting and the lug clip, and operating personnel will inconveniently sleeve the lug clip on the pipe fitting. In addition, during installation, the lug clip is moved to an expected position on the pipe fitting, the lug clip needs to be located by one hand, and the fastening part needs to be further deformed by the other hand with a lug clip clamping tool to fasten the lug clip until an expected clamping pressure is achieved.
With regard to the lug clip, a hoop body with a normal-specification hoop inner diameter needs to be produced in advance, and the fastening part is pre-deformed in a production state to reduce the inner diameter of the lug clip and enable the inner diameter of the lug clip to be more approximate to the outer diameter of the pipe fitting but not equal to the outer diameter of the pipe fitting, so as to realize that an anti-loosing effect is achieved when the lug clip is pre-fixed to the pipe fitting, so that the lug clip is assembled on the pipe fitting with basically no clearance, and then secondary clamping needs to be carried out on the fastening part when the hoop body arriving at the expected position is finally fixed, so that secondary shrinking is carried out on the whole hoop body, and the hoop body is completely locked with the pipe fitting while achieving a limit degree. Therefore, secondary clamping and shrinking treatment is carried out on the fastening part, and is time-wasting and labor-wasting, thus the overall production efficiency will be greatly reduced and production cost will be increased. Moreover, different operation table surfaces are needed for carrying out secondary clamping on the fastening part, thus the accuracy is greatly reduced. What's more, because the fastening part is sequentially subjected to secondary deformation, it is difficult to control an applying force, thus the risk of breakage of the lug clip is greatly increased, and then the instability of installation and fastening for the lug clip is caused.
Another Chinese patent with an application number of CN201520555541.0 discloses an anti-loosing hoop for a pipe fitting. The anti-loosing hoop comprises a clamping belt 1, wherein the clamping belt 1 is bent to be circular and provided with a superposed part 11; the superposed part 11 comprises an outer part and an inner part; and through clamping connection and pre-fixing between upper hook-shaped parts of the inner part and upper damping grooves of the outer part, and clamping for side legs, that is, clamping lugs, arranged on the outer part, the anti-loosing hoop is deformed to be tightened up as a whole, thus the inner diameter and the outer diameter are reduced.
At this moment, a relative action force between the hook-shaped parts and the clamping grooves is increased. Because it is difficult to control a clamping force on the clamping lugs, specifically, as shown in FIG. 5, a stroke from a second clamping connection element 42 to a second locking resisting side 521 is equal to a stroke from a first clamping connection element 41 to a first locking resisting side 511; and because the first locking side 511 is closer to a fastening part 122 relative to the second locking side 521 when the fastening part 122 is clamped, the first locking side 511 is stressed at first, and is more liable to break, thus the whole lug clip is liable to break, and then the whole hoop is broken to fail, and unnecessary waste is caused.